no aavso check stars available for image when plenty available in table form?

am beginner so apols if this is basic!

i am trying to practice with image of RX AND as this was top of the list of easy variables to try.
i used GRAS 001. images are 180 secs long and i have clear, U and R images to work with.
the relevant AAVSO chart looks to be 4950atce and on this there are a number of stars marked 143, 122, 118 etc.
when i open my image and ask for variables to be marked VPHOT marks Rx And in green.
when i ask for comparison stars i get a message saying that none are available or that the AAVSO Service may not be available.
i was surprised that RX And would not have any comp stars in an image that is the same as the chart and approx half a degree wide.
when i select "show aavso sequence" - ie ask for the tabular data this appears without a problem in table form with plenty of comp stars

am i missing something i need to do to get the aavso comp stars to display on my image?